Weak current signal amplification circuit and extraction circuit

Abstract

The invention provides a weak current signal amplifying circuit which comprises a (1-N) th amplifying current mirror, a (1-N-1) th reference current branch and an Nth reference current branch, the (1-N) th amplifying current mirror, the (1-N) th reference current branch and the Nth reference current branch are connected in series, the (1-N) th reference current branch and the Nth reference current branch are connected in parallel with the input end of a (2-N) th amplifying current mirror respectively, and the Nth reference current branch is connected in parallel with the output end of the amplifying circuit. The small effective current amplification for reducing the reference current step by step can be realized, and the small effective current signal is amplified under the condition that the reference current is not greatly changed.

Description

technical field [0001] The invention belongs to the field of weak current signal amplifying circuits, and more particularly, relates to an amplifying circuit of small effective current superimposed on a large reference current. Background technique [0002] There are two general methods for weak current detection technology: one is to use an operational amplifier with low noise and low drift current, which is connected to the structure of a transimpedance amplifier to convert the current signal into a voltage signal. The formula for I / V conversion can be recorded as Vout=I*Rf. The other is described in Patent 201710533994.7. In order to facilitate the integration of the feedback resistance in the transimpedance amplifier, the current mirror is first used to amplify the current, and then the transimpedance amplifier is used for I / V conversion. [0003] For a signal with a small signal loaded on a large current reference, the current reference can be regarded as a common-mode...

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Problems solved by technology

[0004] However, in the field of sensors, if the effective signal is at the pA level and the current reference is at the microampere level, the gap between the effective signal and the DC reference is 10^6, and the existing technology has the following problems: Problem 1, picoampere The level signal is loaded on the microampere level current reference. In order to amplify the picoampere level signal, a high magnification must be used, and a transimpedance amplifier circuit is directly used. The current reference will directly saturate the operational amplifier, and the weak current cannot be extracted; the problem 2. After the subtractor is used to remove the microampere current, if I / V conversion is directly used, there will be noise problems caused by difficult integration and excessive Rf resistance. If a current mirror is used for amplification, picoampere current will appear to make the current mirror Working in the sub-threshold region, the current becomes exponential, and the purpose of amplifying the current cannot be achieved

[0005] Therefore, it is necessary to solve the amplification problem of current sensor picoamp level weak current signal loaded on a large current reference

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